The reason why various forms of apparatus have been suggested for fracturing rocks is to be able to provide a means which, unlike an explosive, will cause fracture but will not cause the material to be projected from the site. Amongst earlier attempts to fracture materials in this way reference can be had to U.S. Pat. No. 4,123,108 in the name of Eric V. Lavon in which a material such as rock is broken by forcing a longish mass body of relatively incompressible fluid, such as water, against the material to be broken, or U.S. Pat. No. 4,141,592 also in the name of Eric V. Lavon in which the rock is broken by maintaining a column of relatively incompressible fluid in a tube the inner end of which is inserted in a predrilled hole in the rock and then generating pressure in the column by means of a piston applied to the tube outside of the hole, which pressure is transmitted through the column to the fluid in the hole.
It has also been proposed in Australian Pat. No. 163,489, Imperial Chemical Industries Limited, to fill a hole drilled into rock or the like with an incompressible liquid and to then use an explosive to provide a shock wave in the material.
Reference is also to be had to Australian Pat. No. 500,571 filed by myself on the 3rd December, 1974 which was designed specifically to use a fracture method in which a shock wave was applied to an incompressible liquid sealed in a hole drilled into a rock or the like which is to be broken. An object of that invention was to achieve safety by preventing the force generated to fracture the rock from hurling fragments of the rock for a considerable distance as is the case in blasting or the like, and this object was achieved by providing apparatus which can be sealed into the hole sufficiently securely to avoid ejection of the device when the shock is applied and at the same time to cause fracture by the shock applied to the rock or other fracturable material. That earlier device utilized a tool which was both anchored in a hole drilled in the rock or the like and which was provided which sealing means to prevent egress of fluid placed under pressure in the hole.
It was known prior to my earlier invention referred to above to use a tool which could be sealed in a hole drilled in the materials to be fractured and reference can be had to U.S. Pat. No. 2,840,360 in the name of Jean Jerusel which utilized a series of expansible resilient rings between sections of the tool and the wall of the hole to prevent high pressure liquid such as water injected into the hole for mining purposes from leaking from the hole, but my earlier invention varied from this by using both a split collet and resilient sealing means, the split collet being expanded in the rock to prevent withdrawal of the tool and the resilient sealing means being compressed to form a tight junction with the wall of the hole to ensure that liquids cannot bypass the tool.
In my invention both of these members were hydraulically actuated in an independent manner and while satisfactory for the purpose it is the object of the present invention to provide an improved form of tool of simple construction which can be readily inserted into a hole drilled into a rock or fracturable member, which can then be locked therein to completely seal the hole, and which can readily be released after use, the present invention avoiding the need to use pressure fluid to actuate the holding collet and the liquid seal.
The device according to this invention thus comprises a tool which is adapted to be connected to a liquid pressure supply firstly to fill a hole in which the tool is inserted and secondly to apply the necessary high pressure shock to the fluid to fracture the rock, the tool comprising a hollow stem with a tapered section at its remote end and means at the other end to connect the liquid supply, the hollow stem having on it a collet which is split so that it can be expanded when relative movement between the stem and the collet takes place, the pressure to expand the collet being obtained by using a member which engages a thread on the stem and draws the stem upwardly in relation to the collet, a sleeve extending from the top of the collet around the stem to be engaged by the thread operated means to hold the collet in position when the stem is moved upwardly in the sleeve.
The stem is also encircled by a resilient sealing member which is so arranged that it can be compressed either by being positioned between the collet and the aforesaid sleeve or it can be compressed independently by a further sleeve encircling the first sleeve and provided with means such as a screw thread on the first sleeve and a nut engaging the second sleeve to allow the seal to be compressed.